Sputum is smelly, generally speaking, because there is purulent inflammation in the lungs or bronchi, and often this inflammation may have accumulated for a long time, and there may have been a chronic infection, so that the sputum will be smelly during an acute attack. In this case, it is common to see diseases such as bronchial dilatation or lung abscess, where there is more purulent sputum in the area, and the sputum may be smelly due to the bacterial content and decaying tissue. In this case, it is necessary to actively discharge the sputum, the more smelly the sputum is, the more toxins in it. If the phlegm is not discharged in time and absorbed back, it will be very harmful to the body. In addition, do not cough vigorously when excreting phlegm, because such phlegm may cause inflammation to spread to other parts if it is squeezed when coughing or splashed into the lung tissue or trachea that is not diseased, so choose good phlegm medicine to actively excrete phlegm at this time.